Microencapsulated electrophoretic electrostatically addressed media for drawing device applications

ABSTRACT

A display includes an encapsulated display media, a rear electrode, and a movable electrode. The encapsulated display media comprises a plurality of capsules, each capsule comprising a plurality of particles dispersed in a fluid. The display media has a first surface and a second surface. The rear electrode is disposed adjacent the second surface of the display media. The movable electrode and the rear electrode apply an electric field across the display media.

RELATED APPLICATION

This invention is a divisional of and claims priority to, U.S. patentapplication Ser. No. 09/310,300, filed on May 12, 1999, which in turn,claims priority to provisional application U.S. Ser. No. 60/085,096filed on May 12, 1998.

FIELD OF THE INVENTION

This invention is related to a display device, and more specifically toa drawing device.

BACKGROUND OF THE INVENTION

An erasable drawing device is known. An erasable drawing device,typically, consists of a blackboard, paper pad, or white board, and anerasable marking device such as a chalk, pencil or dry-erasable marker.

One drawback of such drawing device is that the marking device candissipate, requiring replacement. Another drawback is that the markingdevice can make marks on surfaces other than the screen of the drawingdevice, thereby creating a mess. Still another drawback is that thescreen may not erase completely even with cleansers and vigorouserasing.

An electronic drawing device overcomes some the problems describedabove. An electronic drawing device, typically, includes a touch screenand appropriate logic to cause an underlying electronic display toupdate its image in response to the motion of a stylus. The device, forexample, includes a graphics input pad having an array of transparentcapacitive pixels, which change their capacitance in response to aconductive tipped stylus passing over the pad. The change in capacitanceis sensed and used to address an LCD matrix. A drawback of thiselectronic drawing device is that it requires sophisticated electronicsand significant amount of power. U.S. Pat. No. 4,639,720 describes anelectronic drawing device.

A magnetophoretic display, typically used as children's drawing toy, isanother example of an erasable drawing device. In a magnetophoreticdisplay, a stylus used to write on the display contains a magnet, and acontrast media on the display contains black ferrous material and whitetitanium dioxide. The magnetophoretic display requires no power.However, the magnetophoretic display does not typically permit the userto selectively erase portions of a drawing on the display, unless theuser is able to access both the front and back of the magnetophoreticmedia. Typically, manufacturers of magnetophoretic displays simplyprovide access to only one surface. The display is erased using asliding bar magnet embedded behind the magnetophoretic media. Therefore,the display cannot be selectively erased.

An electrostatically-addressed liquid crystal display is another type ofdrawing device known in the art. Liquid crystal drawing devices,however, suffer from poor image duration due to dissipation of thesurface static charge which maintains the image. With higher voltagesand additional resistive layers, it is possible to extend imageduration, but even then, a duration exceeding 30 minutes is consideredstate of the art. U.S. Pat. Nos. 5,351,143 and 5,117,297, describeliquid crystal drawing devices.

An electrophoretic display is also used as a drawing device. In anelectrophoretic drawing device, electrophoretic particles in a displaymedia of the device migrate toward or away from the drawing surface ofthe device upon application of an electric field across the displaymedia. For example, the drawing device can contain a back electrodecovered by an electrophoretic coating. To write, a positive voltage isapplied to the back electrode and a stylus contacting theelectrophoretic coating is set at ground. The stylus acts as a topelectrode in a local area. A voltage potential is created between thestylus and the back electrode which causes migration of theelectrophoretic particles and a color change of the device. The overallsystem may be covered with a dielectric or anisotropic top layer thatprotects the electrophoretic media. Chiang et al. “A Stylus WritableElectrophoretic Display Device,” Society for Information Display 1979Digest describes an electrophoretic drawing device. Althoughelectrophoretic displays offer excellent contrast and brightness as wellas favorable electrical properties and image duration, electrophoreticdisplays have not been broadly commercialized due to difficulty inmanufacture and lifetime issues related to particle agglomeration andmigration within the display.

SUMMARY OF THE INVENTION

In one aspect, the invention features a display. In one embodiment, thedisplay comprises an encapsulated display media having a first surfaceand a second surface, a rear electrode disposed adjacent the secondsurface of the display media, and a movable rear electrode disposedadjacent the second surface of the display media, and a movableelectrode. The display media comprises a plurality of capsules, eachcapsule comprising a plurality of particles dispersed in a fluid. Themovable electrode, in conjunction with the rear electrode, applies anelectric field across the display media.

In one detailed embodiment, the movable electrode comprises a writingdevice. The writing device can comprise a charge generator. The chargegenerator can comprise an electronic circuit capable of increasing avoltage from about 20 V to about 1000 V. The charge generator canfurther comprise an electronic circuit, which reduces an applied voltageto zero after a predetermined time interval. The writing device cancomprise a charge storage device. The writing device can comprise astylus. For example, the stylus can comprise an electrode tip disposedwithin a curved end of the stylus. The stylus can further comprise aplurality of concentric electrodes. The writing device can include anactivator, such as a piezoelectric device, which activates the chargegenerator. The writing device can have a first end and a second end. Thedisplay media displays a first color when the first end is disposedadjacent the first surface of the display media and a second color whenthe second end is disposed adjacent the first surface of the displaymedia.

In another detailed embodiment, the movable electrode comprises aneraser. In still another detailed embodiment, the movable electrodecomprises a user touching the first surface of the display media. Instill another detailed embodiment, the movable electrode comprises asliding bar, which slides across the first surface of the display media.The sliding bar can include a charge generator, an activator whichactivates the charge generator, an electrostatic print head, and/or ascanner. The charge generator can be a Van de Graaff device, atriboelectric mechanism, or a hand-driven electric generator. Thesliding bar can communicate with a data storage device. Alternatively,the sliding bar can comprise a data storage device.

In still another detailed embodiment, the movable electrode comprises aswitch, which reverses an electric field applied to the display mediaupon activation of the switch. For example, a color displayed on thefirst surface of the display media can change upon activation of theswitch.

In one embodiment, the rear electrode comprises a first region having avoltage different from a voltage of the movable electrode and a secondregion having a voltage matching the voltage of the movable electrode.In another embodiment, the rear electrode comprises a conductivepattern. In still another embodiment, the display media comprises aplurality of electrophoretic particles comprising a plurality of colors,and the rear electrode comprises a plurality of pixel electrodes, eachpixel electrode being set at a voltage for displaying particles of aselected color on the first surface of the display media. Alternatively,the rear electrode can be movable.

In another detailed embodiment, the display further comprises atouchscreen disposed adjacent the first surface or the second surface ofthe display media. The touchscreen can be laminated to the displaymedia.

In another embodiment, the display comprises a display media forming acontinuous loop, and an electrode disposed inside the continuous loop ofthe display media. In one detailed embodiment, the display furthercomprises a case containing the display media and the electrode. Thecase has a first surface and a second surface. The first surfacecomprises a protective layer and serves as a writing surface. In anotherdetailed embodiment, the display further comprises a movable electrode.The removable electrode, in conjunction with the electrode, applies anelectric field across the display media.

In still another embodiment, the display comprises a display mediahaving a first surface and a second surface, an electrode disposed onthe first surface of the display media, and a photoconductor disposed onthe second surface of the display media. The display media displays areplica of an image shown on a substrate when the photoconductor isprovided adjacent the substrate. In one detailed embodiment, thesubstrate comprises an emissive display such as a computer screen or atelevision screen. In another detailed embodiment, the substratecomprises a reflective display. The reflective display can be a piece ofpaper. In another detailed embodiment, the display further comprises alight source for illuminating the substrate.

In another aspect, the invention features a method for creating an imageon a display. The method comprises the steps of: (a) providing a displaycomprising an encapsulated display media comprising a plurality ofcapsules, each capsule comprising a plurality of particles dispersed ina fluid, the display media having a first surface and a second surfaceand a rear electrode disposed on the second surface of the displaymedia; (b) placing a movable electrode adjacent the first surface of thedisplay media; and (c) applying an electric field across the displaymedia through the movable electrode and the rear electrode, therebycreating an image on the first surface of the display media.

In another aspect, the invention features a method for reproducing animage. The method comprises the steps of: (a) providing a displaycomprising: a1) a display media comprising a first surface and a secondsurface, a2) an electrode disposed on the first surface of the displaymedia, and a3) a photoconductor disposed on the second surface of thedisplay media; and (b) placing the photoconductor adjacent a substratecomprising an image, thereby reproducing the image from the substrate onthe display media.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention, as well as the invention itself, will be more fullyunderstood from the following description of preferred embodiments, whenread together with the accompanying drawings, in which:

FIG. 1a shows a cross-sectional view of a display according to oneembodiment of the invention.

FIG. 1b shows a partial cross-sectional view of a display according toone embodiment of the invention.

FIG. 1c is a chart providing two series of triboelectric elements.

FIG. 2 shows a cross-sectional view of a stylus for addressing a displayaccording to one embodiment of the invention.

FIG. 3a shows a cross-sectional view of a stylus for addressing adisplay according to one embodiment of the invention.

FIG. 3b shows a bottom view of the stylus of FIG. 3a.

FIG. 4a shows a schematic view of a stylus for addressing a displayaccording to one embodiment of the invention.

FIG. 4b shows a cross-sectional view of a stylus for addressing adisplay according to one embodiment of the invention.

FIG. 4c shows a cross-sectional view of a stylus for addressing displayaccording to one embodiment of the invention.

FIG. 4d shows a cross-sectional view of a stylus for addressing adisplay according to one embodiment of the invention.

FIG. 4e shows a schematic view of a stylus for addressing a displayaccording to one embodiment of the invention.

FIG. 5 shows a cross-sectional view of a display according to oneembodiment of the invention.

FIG. 6 shows a perspective view of a display according to one embodimentof the invention.

FIG. 7a shows a perspective view of a display according to oneembodiment of the invention.

FIG. 7b shows a perspective view of a display system according to oneembodiment of the invention.

FIG. 8a shows a perspective view of a display according to oneembodiment of the invention.

FIG. 8b shows a simplified circuit diagram of the display of FIG. 8a.

FIG. 9a shows a perspective view of a display used with a writingimplement according to one embodiment of the invention.

FIG. 9b shows a perspective view of a display comprising a drawing madewith the writing implement of FIG. 9a according to one embodiment of theinvention.

FIG. 9c shows a plan view of a writing implement according to oneembodiment of the invention.

FIG. 9d shows a cross-sectional view of a drawing implement and a stylusaccording to one embodiment of the invention.

FIG. 10 shows a cross-sectional view of a display according to oneembodiment of the invention.

FIG. 11 shows a perspective view of a display according to oneembodiment of the invention.

FIG. 12a shows a plan view of a display according to one embodiment ofthe invention.

FIG. 12b shows a cross-sectional view of a portion of a displayaccording to one embodiment of the invention.

FIG. 13 shows a cross-sectional view of a portion of a display accordingto one embodiment of the invention.

FIG. 14a shows a cross-sectional view of a portion of a displayaccording one embodiment of the invention.

FIG. 14b illustrates the rear electrodes of the display of FIG. 14a.

FIG. 14c shows a cross-sectional view of a portion of a displayaccording one embodiment of the invention.

FIG. 15a shows a cross-sectional view of a display according to oneembodiment of the invention.

FIG. 15b shows a perspective view of a display according one embodimentof the invention.

FIGS. 16a-16 f show various methods of addressing a display with anelectrode.

FIG. 17 shows a cross-sectional view of a display according to oneembodiment of the invention.

DETAILED DESCRIPTION

Referring to FIG. 1a, a display 10 includes a casing 12, a rearelectrode 14 disposed inside the casing 12, an encapsulated displaymedia 16 disposed adjacent the rear electrode 14, a protective layer 18disposed adjacent the display media 16, and a movable electrode 20. Thedisplay 10 can be used as a drawing system. The protective layer 18serves as a drawing surface. The movable electrode 20 comprises a chargeconducting mechanism. In one embodiment, the movable electrode 20 is awriting device. In the embodiment of FIG. 1, the writing device 20comprises a stylus. Alternatively, the display 10 of the presentinvention can be addressed mechanically by means of a robotic arm orcharge-carrying print head that is moved relative to the drawingsurface. For example, an electrostatic printer can be used to draw onthe drawing surface. When the movable electrode 20 contacts the drawingsurface 18, the movable electrode 20 and the rear electrode 14 apply anelectric field across the display media 16, and thereby display an imageon the drawing surface 18 of the system 10.

In one embodiment, the casing 12 is made from a plastic containercapable of holding the display media 16, the rear electrode 14, and anynecessary electronics. Alternatively, the casing 12 can be made of anyother material. The casing 12 may be of any size, ranging from small fortoy applications and large for applications in presentation displays.The casing 12 can also include compartments for storing the drawinginstrument 20 and other accessories such as an eraser.

In one embodiment, the encapsulated display media 16 includes aparticle-based display media. In one detailed embodiment, theparticle-based display media is made from an electronic ink. Anelectronic ink is an optoelectronically active material which comprisesat least two phases: an electrophoretic contrast media phase 17 and acoating/binding phase 19. The electrophoretic phase 17 includes, in someembodiments, a single species of electrophoretic particles dispersed ina clear or dyed medium, or more than one species of electrophoreticparticles having distinct physical and electrical characteristicsdispersed in a clear or dyed medium. In some embodiments theelectrophoretic phase 17 is encapsulated, that is, there is a capsule 13wall phase between the two phases.

The optical quality of an electronic ink is quite distinct from otherelectronic display materials. The most notable difference is that theelectronic ink provides a high degree of both reflectance and contrastbecause it is pigment based (as are ordinary printing inks). The lightscattered from the electronic ink comes from a very thin layer ofpigment close to the top of the viewing surface. In this respect itresembles an ordinary, printed image. Also, electronic ink is easilyviewed from a wide range of viewing angles in the same manner as aprinted page, and such ink approximates a Lambertian contrast curve moreclosely than any other electronic display material. Since electronic inkcan be printed, it can be included on the same surface with any otherprinted material, including traditional inks. Electronic ink can be madeoptically stable in all display configurations, that is, the ink can beset to a persistent optical state. Fabrication of a display by printingan electronic ink is particularly useful in low power applicationsbecause of this stability.

In one embodiment, a capsule 13 is filled with a plurality of particlesand a dyed suspending fluid. In one detailed embodiment, the particlesare titania particles. When a direct-current electric field of theappropriate polarity is applied across the capsule 13, the particlesmove to the drawing surface 18 and scatter light. When the appliedelectric field is reversed, the particles move to the rear surface ofthe display media 16 and the drawing surface then appears dark.

In another detailed embodiment, the capsule 13 includes a first set ofparticles and a second set of particles in the capsule 13. The first setof particles and the second set of particles have contrasting opticalproperties. For example, the first set of particles and the second setof particles can have differing electrophoretic mobilities. In addition,the first set of particles and the second set of particles can havecontrasting colors. For example, the first set of particles can bewhite, while the second set of particles can be black. The capsulefurther includes a substantially clear fluid. The capsule has a rearelectrode 14 on one side and a writing instrument comprising anelectrode on the other side. The electrodes 13, 20 are connected to asource of voltage (not shown), which may provide an alternating-current(AC) field or a direct-current (DC) field to the capsule 13. Uponapplication of an electric field across the electrodes 13, 20, the firstset of particles move toward the drawing surface 18, while the secondset of particles move toward the rear electrode 14.

In another detailed embodiment, the display media 16 is formed with asuspended particle display media. The suspended particle display mediaincludes needle-like particles in a transparent fluid. The particleschange their orientation upon application of an AC field across theelectrodes. When the AC field is applied, the particles are orientedperpendicular with respect to the drawing surface 18 and the surfaceappears transparent. When the AC field is removed, the particles arerandomly oriented and the display drawing surface 18 appears opaque.Commonly-owned, co-pending U.S. patent application Ser. No. 09/140,792filed on Aug. 27, 1998, which describes electrophoretic displays, isincorporated herein by reference.

Electronic ink displays are novel in that they can be addressed by DCvoltages and draw very little current. As such, the conductive leads andelectrodes used to deliver the voltage to electronic ink displays can beof relatively high resistivity. The ability to use resistive conductorssubstantially widens the number and type of materials that can be usedas conductors in electronic ink displays. In particular, the use ofcostly vacuum-sputtered indium tin oxide (ITO) conductors, a standardmaterial in liquid crystal devices, is not required. Aside from costsavings, the replacement of ITO with other materials can providebenefits in appearance, processing capabilities (printed conductors),flexibility, and durability. Additionally, the printed electrodes are incontact only with a solid binder, not with a fluid layer (like liquidcrystals). This means that some conductive materials, which wouldotherwise dissolve or be degraded by contact with liquid crystals, canbe used in an electronic ink application. These include opaque metallicinks for the rear electrode (e.g., silver and graphite inks), as well asconductive transparent inks for either substrate. These conductivecoatings include conducting or semiconducting colloids, examples ofwhich are indium tin oxide and antimony-doped tin oxide. Organicconductors (polymeric conductors and molecular organic conductors) alsomay be used. Polymers include, but are not limited to, polyaniline andderivatives, polythiophene and derivatives,poly3,4-ethylenedioxythiophene (PEDOT) and derivatives, polypyrrole andderivatives, and polyphenylenevinylene (PPV) and derivatives. Organicmolecular conductors include, but are not limited to, derivatives ofnaphthalene, phthalocyanine, and pentacene. Polymer layers can be madethinner and more transparent than with traditional displays becauseconductivity requirements are not as stringent.

In one embodiment, the display media 16 includes a binder material whichbinds the capsules 17 together. The binder is used as a non-conducting,adhesive medium supporting and protecting the capsules, as well asbinding the electrode materials to the capsule dispersion. Binders areavailable in many forms and chemical types. The coating/binding phase 19includes, in one embodiment, a polymer matrix that surrounds theelectrophoretic phase 17. In this embodiment, the polymer in thepolymeric binder is capable of being dried, crosslinked, or otherwisecured as in traditional inks, and therefore a printing process can beused to deposit the electronic ink onto a substrate. In anotherembodiment, the binder material can be water-soluble polymers,water-borne polymers, oil-soluble polymers, thermoset and thermoplasticpolymers, or radiation-cured polymers.

Among the water-soluble polymers are the various polysaccharides, thepolyvinyl alcohols, N-methyl Pyrollidone, N-vinyl pyrollidone, thevarious Carbowax® species (Union Carbide, Danbury, Conn.), andpoly-2-hydroxyethylacrylate.

The water-dispersed or water-borne systems are generally latexcompositions, typified by the Neorez® and Neocryl® resins (ZenecaResins, Wilmington, Mass.), Acrysol® (Rohm and Haas, Philadelphia, Pa.),Bayhydrol® (Bayer, Pittsburgh, Pa.), and the Cytec Industries (WestPaterson, N.J.) HP line. These are generally latices of polyurethanes,occasionally compounded with one or more of the acrylics, polyesters,polycarbonates or silicones, each lending the final cured resin in aspecific set of properties defined by glass transition temperature,degree of “tack,” softness, clarity, flexibility, water permeability andsolvent resistance, elongation modulus and tensile strength,thermoplastic flow, and solids level. Some water-borne systems can bemixed with reactive monomers and catalyzed to form more complex resins.Some can be further cross-linked by the use of a crosslinking reagent,such as an aziridine, for example, which reacts with carboxyl groups.

A typical application of a water-borne resin and aqueous capsulesfollows. A volume of particles is centrifuged at low speed to separateexcess water. After a given centrifugation process, for example 10minutes at 60×G, the capsules are found at the bottom of the centrifugetube, while the water portion is at the top. The water portion iscarefully removed. The mass of the remaining capsules is measured, and amass of resin is added such that the mass of resin is between one eighthand one tenth of the weight of the capsules. This mixture is gentlymixed on an oscillating mixer for approximately one half hour. Afterabout one half hour, the mixture is ready to be coated onto theappropriate substrate.

The thermoset systems are exemplified by the family of epoxies. Thesebinary systems can vary greatly in viscosity, and the reactivity of thepair determines the “pot life” of the mixture. If the pot life is longenough to allow a coating operation, capsules may be coated in anordered arrangement in a coating process prior to the resin curing andhardening.

Thermoplastic polymers, which are often polyesters, are molten at hightemperatures. A typical application of this type of product is hot-meltglue. A dispersion of heat-resistant capsules could be coated in such amedium. The solidification process begins during cooling, and the finalhardness, clarity and flexibility are affected by the branching andmolecular weight of the polymer.

Oil or solvent-soluble polymers are often similar in composition to thewater-borne system, with the obvious exception of the water itself. Thelatitude in formulation for solvent systems is enormous, limited only bysolvent choices and polymer solubility. Of considerable concern insolvent-based systems is the viability of the capsule itself—theintegrity of the capsule wall cannot be compromised in any way by thesolvent.

Radiation cure resins are generally found among the solvent-basedsystems. Capsules may be dispersed in such a medium and coated, and theresin may then be cured by a timed exposure to a threshold level ofultraviolet radiation, either long or short wavelength. As in all casesof curing polymer resins, final properties are determined by thebranching and molecular weights of the monomers, oligomers andcrosslinkers.

A number of “water-reducible” monomers and oligomers are, however,marketed. In the strictest sense, they are not water soluble, but wateris an acceptable diluent at low concentrations and can be dispersedrelatively easily in the mixture. Under these circumstances, water isused to reduce the viscosity (initially from thousands to hundreds ofthousands centipoise). Water-based capsules, such as those made from aprotein or polysaccharide material, for example, could be dispersed insuch a medium and coated, provided the viscosity could be sufficientlylowered. Curing in such systems is generally by ultraviolet radiation.

In one detailed embodiment, the binder material renders the displaymedia elastomeric. For example, a binder material including polyurethanecan render the display media elastomeric. In another embodiment, thebinder material renders the display media brittle. For example, a bindermaterial comprising an epoxy can render the display media brittle. Inanother embodiment, the binder material has ultraviolet light protectiveproperties, for example, by incorporated ultraviolet light absorbers,such as benzotriazole derivative material, in the binder. A displaymedia having an elastomeric and/or UV protective material increasesdurability and lifetime of the display 10.

Encapsulation of the electrophoretic suspension serves as a superiormedia for use in drawing devices and as a substrate for electrostaticprinting. The benefits of microencapsulation for such purposes derivefrom the polymeric nature of the microcapsule wall and surroundingbinder, which offers greater structural integrity than anon-encapsulated electrophoretic suspension. In addition, encapsulatedelectrophoretic suspensions overcomes the problems encountering by priorelectrophoretic drawing devices in which support walls were used asspacers. These walls cause gaps in the image and reduce the totaladdressable portion of the display. A microencapsulated electrophoreticmedia is inherently supported and does not require suchimage-interrupting walls. Therefore, it is possible to achieve acontinuous image tracing.

In addition, the encapsulated display media 16 can be coated directlyonto a plastic substrate in a process which offers a means of economicalproduction for large surface areas. Furthermore, encapsulated displaymedia 16 can be made flexible or set into curves and contours. Thisoffers new manufacturing processes and design capabilities.

Although encapsulated electrophoretic drawing system requires someelectrical charge, it operates by field effect and hence draws minimalpower. Further, some electrophoretic systems exhibit bistability suchthat once they are addressed to a dark or light state, they stay dark orlight without any further power requirement, and some systems can evenmaintain a gray state without power. Such images can last for severalmonths or more without requiring any further power.

In one embodiment, the protective layer 18 is made from lexan,polycarbonate, or mylar. In another embodiment, the protective layer 18includes an ultraviolet light protective coating. For example, thecoating can be imbued with UV-protective polymer material such aspolyvinylfluoride or LEXAN HP12W (polycarbonate base) or other lightstabilizing additives such as Benzotriazole or Hydroperoxide decomposer(e.g., HALS, Hindered Benzoate and Phosphite), or combination of thesematerials. In another embodiment, the protective layer 18 is a scratchresistant coating. In still another embodiment, the protective coating18 is made from a material, which reduces grease and oil build-up on thescreen surface.

Referring to FIG. 1a, the display 10 further includes acharge-generating mechanism (not shown). The charge-generating mechanismcan be incorporated in the casing 14, or the movable electrode 20. Inone embodiment, the charge-generating mechanism is a battery and anelectronic circuit, which is capable of increasing a voltage into arange from 20 volts to 1000 volts or more, and more preferably from 100volts to 500 volts. In another embodiment, the charge-generatingmechanism includes a circuit which automatically reduces an appliedvoltage to zero after a pre-determined period of time to preservebatteries. In another embodiment, the charge-generating mechanism has asafety mechanism to prevent shocking the user. For example, thecharge-generating mechanism can use resistors to limit maximum currentdrawn from the charge-generating mechanism. In general, the resistanceshould be sufficient to keep the generated current to a level below thatwhich can be felt by the user. In still another embodiment, thecharge-generating mechanism can have an interlock mechanism. Theinterlock mechanism prevents the user from simultaneously contacting thewriting instrument and another charge-carrying device such as an eraserto be described. For example, at least one of the terminals of thewriting instrument and the eraser can be adapted to disconnect when theuser comes in contact with both.

In another embodiment, the display 10 includes means for generating anelectrostatic charge, such as Van de Graff generator, fluid pumps, ortriboelectric forces. A Van de Graff generator generates high voltage byproviding physical separation of charge through a belt. A fluid pumpgenerates high voltage by providing physical separation of chargethrough fluid displacement. FIG. 1b illustrates a display 10′ using atriboelectric force. The system 10′ includes a rear electrode 14′ inelectrical communication with a slider 3. The slider 3 slides across theprotective layer 18′, thereby generating a static charge. The staticcharge can be stored in a capacitor and discharged as the user writes.This embodiment does not require a battery. FIG. 1c is a chart providingtwo series of triboelectric elements from which an appropriate slidermaterial and the protective layer can be selected.

In one embodiment, the display 10 has an intervening dielectric layer.The dielectric layer can be placed between the protective layer 18 andthe display media 16, be incorporated into the protective layer 18, orbe incorporated into the binder material. The dielectric layer can storeelectric charge long enough to address the display media, withoutbleeding the charge. The dielectric layer also allows applied voltage topass through the layer and reach the display media. In this manner, thewriting speed on the writing device can be increased, since the writingdevice need not be positioned above the display media for a durationnecessary to address the display media. In one embodiment, thedielectric layer is fabricated from a cross-linked polymer layer. In onedetailed embodiment, the dielectric layer is fabricated from a film madeof, for example, polyethylene phthalate, polyethylene naphthalate,polypropylene, polyethylene, polyvinylchloride, polysulfone,polyphnylene oxide, ionomer, polycarbonate, nylon or fluororesin layeredwith a bond or adhesive or such.

Referring to FIG. 2, a stylus 20′ comprises an elongated probe 22 with atip 24. In one embodiment, the tip 24 may be shaped small to permitdrawing of a fine line. The tip 24 includes an electrode 26 which isflush with a surface of the tip 24. In some embodiments, the electrode26 encompasses a smaller area than the tip 24. The electrode 26 isconnected to a voltage source (not shown) through a wire 21. In someembodiments, the tip 24 is rounded. This configuration of the stylus 20′permits a wider area of the stylus 20′ to come into contact with adrawing surface, while allowing a fine line to be drawn withoutpuncturing the drawing surface. In one embodiment, the electrode 26 iscovered with a dielectric coating, which protects the stylus 20′ andprevents exposure of the electrode 26 to the environment. In anotherembodiment, the tip 24 of the stylus 20′ comprises an elastomericmaterial.

In another embodiment, the stylus includes a damping mechanism such as aspring built into the tip as to cushion the drawing surface from thephysical forces caused by the motion of the user's hand.

FIGS. 3a and 3 b depict another embodiment in which a stylus 20″includes multiple electrodes 26 a, 26 b, 26 c, that are insulated fromeach other. A voltage can be applied to all or any of the electrodes 26a, 26 b, 26 c, thereby controlling the width and shape of the line drawnon the drawing surface. For example, when an electric field is appliedthrough only the electrode 26 a, a thin line is drawn on the drawingsurface. However, when an electric field is applied through both theelectrodes 26 a, 26 b, a thicker line is drawn, and even a thicker lineis drawn when an electric field is applied through all three electrodes26 a, 26 b, 26 c. In one embodiment, the stylus 20″ includes a switch25, and a logic circuit 27 which activates the various electrodes 26 a,26 b, 26 c.

In one embodiment, the width of the line drawn on the drawing system iscontrolled by varying the voltage potential applied across the displaymedia. For example, the duty cycle or the magnitude and/or duration ofvoltage applied can be varied.

FIGS. 4a-4 c depict other embodiments in which a stylus 30 includes acharge-generating device 32 and/or charge-storage device 34. In theembodiments of FIGS. 4a-4 c, the charge-generating device can be a piezoelectric device 32, 32′, 32″ and the charge storage device can be acapacitor 34, 34′, 34″. Alternatively, the display 10″ can include avoltage source 5 and a charge storage device 34 external to the stylus30, as illustrated in FIG. 4e. Referring to FIG. 4b, pressing the stylus30′ against the drawing surface through a natural drawing motionmechanically triggers the piezo electric device 32′ to generate acurrent and to charge the capacitor 34′. Referring to FIG. 4c, a switch35 on the stylus 30″ can be clicked to trigger the piezo electric device32′ to generate a current and to charge the capacitor 34″.

In one embodiment, the stylus includes a switch which permits the userto reverse the electric field applied across the display media, andthereby switch from drawing in one color to drawing in another color.The second color may have the effect of erasing what is drawn using thefirst color. For example, the user can draw in blue on a whitebackground prior to switching, and draw in white on a blue backgroundafter switching. In one example, the voltage applied to the electrode 36can switch from +100 v to −100 v, where the voltage applied to the rearelectrode of the drawing device is 0 v. Alternatively, the voltageapplied to the electrode 36 of the stylus 30 can remain 0 v and thevoltage applied to the rear electrode varied.

Referring to FIG. 4d, the stylus 40 includes two electrodes 42, 44placed at opposite ends of the stylus 40. Different voltages are appliedto each of the electrodes 42, 44, such that electrode 42 allows the userto draw in one color, while electrode 44 allows the user to draw in adifferent color. In another embodiment, a positive voltage can beapplied to electrode 42 to write on the drawing surface, while anegative voltage of the same magnitude can be applied to electrode 44 toerase the drawing on the drawing surface. The switch 45 allows the userto select one of the two electrodes 42, 44. In this embodiment, the rearelectrode is set to ground.

Referring to FIG. 5, a display 50 includes a casing 52, a rear electrode53 disposed inside the casing 52, an encapsulated display media 54disposed adjacent the rear electrode 53, a piezoelectric film 56disposed adjacent the display media 54, and a protective layer 55disposed adjacent the piezoelectric film 56. In this embodiment, thestylus 58 need not be electrically connected to the drawing device 50 orinclude a charge generator. When a force is applied to the piezoelectricfilm 56 by pressing it with the stylus 58, the piezoelectric film 56becomes charged. Thus a voltage potential can be created cross thedisplay media 54 through the piezoelectric film 56 and the rearelectrode 53. The piezoelectric 56 film can comprise a polymericmaterial. For example, the piezoelectric film can comprise vinylidenefluoride homopolymer or a copolymer of vinylidene fluoride and one ormore copolymerizable monomers. The display media 54 includes capsules,each capsule comprising a plurality of particles dispersed in a fluidmedium.

Referring to FIG. 6, a drawing system 60 which is substantially similarto the display of FIG. 1a further includes a piezo electric button 62connected to a capacitor 68. The capacitor is connected to the stylus69. When the user presses the piezo electric button 62, the capacitor 68becomes charged. The system 60 can further include means formechanically storing energy using, for example, a spring andsubsequently transferring the mechanical energy to the piezo electricdevice 62.

Referring to FIG. 7a, a drawing system 70 which is substantially similarto the display of FIG. 1a further includes an eraser 72. The eraser 72is physically connected to the drawing system 70 through a cable 73. Animage created on the drawing surface 71 by applying an electric fieldacross the display media of the drawing system 70 through the writinginstrument (not shown) and the rear electrode (not shown) can be erasedby applying an oppositely charged electric field across the displaymedia through the eraser 72 and the rear electrode. In one embodiment,the eraser 72′ is positioned inside the device casing 74 above thedrawing surface 71 in the form of a sliding bar 76 as shown in FIG. 7b.The sliding bar 76 includes a tab 78, which the user can use to slidethe eraser bar 76 across the drawing surface 71, thereby erasing animage drawn on the drawing surface 71. In one embodiment, the slidingbar 76 has an electrode which can be set to positive or negative voltageto cause the screen to change its color.

Referring to FIG. 8a, a drawing system 80 includes a casing 82, a rearelectrode, an encapsulated display media, a protective layer, and anelectrode surface 84. The protective layer 85 functions as the drawingsurface. In this embodiment, a user touches the electrodes surface 84with his or her first hand 86, while the user writes on the drawingsurface 85 with the second hand 88. In this embodiment, a separatewriting instrument may not be necessary. A voltage source is placedinside the casing 82. Since the human body is electrically conductive,an electric field can be created across the display media through theuser's second hand 88 and the rear electrode. As illustrated in FIG. 8b,a typical skin resistance is about 10 kΩ-500 kΩ. As long as equivalentresistance (R_(EQ)) of display is much higher than the skin resistance,most of the applied field will drop across the system. In oneembodiment, the drawing system 80 has an internal 1 mΩ current limitingresistor (R_(CL)). When 100 V is applied, the resistor (R_(CL)) wouldlimit current flowing though the body and the display system to 100 kΩ.The electrode surface 84 can be a button. Alternatively, the electrodesurface 84 can be a part of a stylus.

In one embodiment, the movable electrode of the present invention canhave a variety of shapes or forms to provide different drawing tips. Forexample, the movable electrode can include a calligraphic tip, brush,sponge, fabric, roller, or elastomeric solid, which is electricallyconnected to a source of charge such an electrode surface, a voltagesource, or a stylus. In another example, the writing instrument cancomprise a non-conductive object coated with a conductive layer. Instill another example, the writing instrument can be cones, shapes andcards. In still another example, the movable electrode can comprise astamp in any shape or form.

Referring to FIGS. 9a-9 d, a writing implement 90 can be used with thedrawing system of the present invention. The writing implement 90 can bein the form of a card. The writing implement 90 includes an invisibleconductive pattern 92 printed on the back side of the card. When thewriting implement 90 is placed on a drawing surface 93 of the drawingsystem 94 a and a voltage is applied to the conductive pattern 92 usinga stylus 95, the conductive pattern leaves a surprise image 96 on thedrawing surface 93. In the embodiment of FIGS. 9a-9 c, the writingimplement 90 includes a cut out hole 91 in the form of letter A. Whenusing this writing implement 90, the user places the writing implement90 on the drawing surface 93 and fills in the letter A using the stylus.An edge of the cut out hole 91 includes a conductor 97 which isconnected to the conductor pattern 92. Thus, when the stylus contactsthe conductor 97, a surprise image 96 corresponding to the conductorpattern 92 appears on the drawing surface. When the drawing implement 90is removed from the drawing surface 93, the letter A remains, but nextto it a picture of an apple 96 is also shown. The embodiment can beuseful as a teaching tool for children.

FIG. 10 depicts an embodiment in which a display 100 has both erasableand non-erasable portions for flexibility. Referring to FIG. 10, thedisplay 100 includes a casing 102, a rear electrode 104, an encapsulateddisplay media 106, a top electrode 108, a protective layer 109, and astylus 107. In this embodiment, a first portion of the drawing device100 is available for the user to draw on, while a second portion of thedrawing device 100 provides a pre-determined image. In the secondportion, the top electrode 108 and the rear electrode 104 apply anelectric field across the display media 106. For example, an animatedfigure can be provided on the drawing surface 109 using this embodiment.A figure holding a “BLUE” sign can appear when the stylus 107 is set todraw in blue, and the “WHITE” sign can appear when the stylus 107 is setto draw in white.

The display of the present invention can be integrated with othermultimedia elements including audio feedback tones or music, to enhancethe drawing experience. For example, a speaker included in the displaycan emit sound when the stylus is toggled from a first voltage to asecond voltage.

Referring to FIG. 11, a display 110 provides multiple drawing surfaces.The display 110 includes a casing 112, a flexible display media 114arranged in a continuous belt loop, a rear electrode 116 disposed insidethe belt loop, and a protective layer 118 serving as a drawing surface.The display media 114 loops around a pair of rollers 119 and a knob 117for rolling the belt loop. In this embodiment, the user can roll betweendifferent drawing surfaces. For example, the user can draw on the firstdrawing surface of the display media 114 a, then roll it to the back inorder to save the drawing, and still have another fresh drawing surface114 b. In one embodiment, the display media 114 comprises anencapsulated electrophoretic display media. In one detailed embodiment,the first drawing surface of the display media 114 a provides a firstcolor combination such as black and white, while the second drawingsurface of the display media 114 b provides a second color combinationsuch as yellow and blue. In another embodiment, the display 110 furtherincludes an eraser 113, which erases the surface of the display media114 as it rolls back.

In one embodiment, a display of the present invention is flexible. Inone detailed embodiment, the flexible display is used as a wallpaperwhich provides a drawing surface. The display can be constructed bycoating a transparent protective layer with an encapsulatedelectrophoretic display media and then laminating this coated structurewith a rear electrode. Examples of flexible, transparent protectivelayer include polyester, polycarbonate, polyvinylfluoride, acrylic, andpolychlorotriflouroethylene. The rear electrode can comprise a flexiblepolymeric conductor material such as conductive particle doped withpolymers, conductive polymers (e.g., polyaniline, polyacetylene,polythiophene), doped polymers, metallized polymers, or polymer filmcoated with conductive material (e.g., metal, metal oxide, conductiveparticle dispersion, and conductive polymer dispersion). In anotherembodiment, the display media and the rear electrode are printed on theprotective layer. Details of the printing methods are described incommonly owned U.S. patent application Ser. No. 08/935,800 filed on Sep.23, 1997, incorporated herein by reference.

In another detailed embodiment, the flexible display can be used as an“electronic paper.” An electronic paper can be used anywhere paper isused today but offers the ability to be updated via stylus, printhead orsimilar means. An electronic paper can be used as reusable fax andcopier paper, re-writable bar-codes, labels and packaging, re-writabledisplays on plastic cards, credit cards, laminated driver's licenses andmagnetic strip cards, reprintable signs and billboards, and reusablenewspapers, magazines, greeting cards and books.

In one embodiment, the encapsulated display media or the display mediain combination with the rear electrode of the drawing system can beremoved and replaced with a fresh display media or display media/rearelectrode combination by the user, such that the user can keep his orher drawings. In another embodiment, the rear electrode of the drawingsystem can be removed and replaced with a different rear electrode. Inthese embodiments, the system may include a connector which provideselectrical communication between a voltage source and the rearelectrode. These removable electrodes would permit a variety of rearelectrode patterns to be used with the drawing system. For example, theelectrode can be patterned to include a first section connected to theground and a second section connected to the stylus potential. In thisembodiment, the first section connected to ground can be revealed whenthe stylus is placed adjacent the first section. This embodiment can beused to create a coloring book. In another example, an outline can beprovided on the drawing surface using this embodiment. The user firstsets the entire drawing surface to display a single color such as blue.A rear electrode having a non-conductive pattern of an outline such as amap is inserted in the drawing system. An electric field is applied tothe display media of the drawing system to change the color of thedisplay from blue to another color, such as white. The outline of themap remains in blue, while the rest of the display becomes white. Theuser can now write on the drawing surface in blue and may write visiblyover the map shown on the drawing surface.

Referring to FIG. 12a, a drawing system 120 permits the user to writeusing a stylus or a charge-generating electrostatic print head 124. Inone embodiment, an electrostatic print head 124 is moved across a fixedelectrophoretic display media to create an image. In one embodiment, theelectrostatic print head 124 senses its location on the drawing system120 such that it can print locally on the display surface. The drawingsystem 120, in this embodiment, can be used as a printer. Theelectrostatic print head 124 can move automatically or manually. Thesystem 120 can further include a speed sensor for detecting manualscanning of the print head.

In one embodiment, a drawing system employs both electrophoretic effectand other means to permit a user to draw on the system. Referring toFIG. 12b, the system 125 includes a casing 126, an encapsulated displaymedia 127 in the form of a belt loop, a rear electrode 128 disposedwithin the belt loop, and a protective coating 129. The system 125further includes an electrostatic printer 123 for providing anunderlying image on the drawing surface 129. In addition, the user canuse a standard dry-erasable marker 121 to draw on the drawing surface129 as is typically used on white boards. Both the underlying image andthe user's markings are visible on the drawing surface 129. In onedetailed embodiment, the drawing system 125 further includes an opticalinput means (e.g., scanner) for scanning a drawing provided by thestandard dry-erasable marker 121.

In one embodiment, the drawing system includes a first region whichdisplays a permanent image and a second region in which the user canwrite on and erase. For example, the drawing system can include a blankmap or a blank calendar. Referring to FIG. 13, the drawing system 130includes the rear electrode separated into multiple regions 132, 134.The first region 132 has a voltage equal to the voltage of the stylus136, such that an electric field cannot be applied across the displaymedia 138 adjacent the first region 132. Therefore, the user cannotwrite on or erase on the first region 132. The second region 134 has avoltage different from the voltage of the stylus 136, such that anelectric field can be applied across the display media 138 adjacent thesecond region 134. The user draws on the second region 134. The drawingsystem 130 can include a rear electrode having an electrode patterncorresponding to an image to be permanently displayed on the drawingsystem 130.

In one embodiment, the drawing system provides multiple opticalproperties, such as permitting the user to draw in multiple colors.Referring to FIGS. 14a and 14 b, the drawing system 140 includes apixelated rear electrode 144. The rear electrode 144 is patterned intomultiple pixel or line electrodes 144 a, 144 b, 144 c. In one detailedembodiment, the pixel or line electrodes 144 a, 144 b, 144 c have awidth of less than about 1 mm. The first electrodes 144 a correspond toa first optical property (e.g., red), the second electrodes 144 bcorrespond to a second optical property (e.g., green), and the thirdelectrodes 144 c correspond to a third optical property (e.g., blue).The drawing system 140 further includes an encapsulated display media146, which includes particles or solvent of different opticalproperties, such as color. For example, the display media 146 caninclude particles or solvent of red, green, and blue, or cyan, magenta,and yellow. In one detailed embodiment, a capsule adjacent the firstelectrode 144 a includes white particles and a red dye, a capsuleadjacent the second electrode 144 b includes white particles and a greendye, and a capsule adjacent the third electrode 144 c includes whiteparticles and a blue dye. In this embodiment, the display media 146adjacent the first electrode 144 a forms a red region 146 a. The displaymedia 146 adjacent the second electrode 144 b forms a green region 146b. The display media 146 adjacent the third electrode 144 c forms a blueregion 146 c.

In order to draw in red, a voltage which differs from the voltage of thestylus 148 is applied to the pixel or line electrodes 144 acorresponding to red. The electrodes 144 a are connected to a common redelectrode. The stylus 148 and the rear electrodes 144 a establish anelectric field across the display media 146, such that white particlesmigrate away from the protective layer 149 and displaying the color ofthe red dye. A voltage that matches the voltage of the stylus 148 isapplied to the pixel or line electrodes 144 b, 144 c corresponding togreen and blue, such that an electric field across the green region 146b and the blue region 146 c cannot be established. The second electrodes144 b are connected to a common green electrode. The third electrodes144 c are connected to a common blue region. The stylus 148, therefore,does not electrophoretically affect any media except the mediacorresponding to the red regions 146 a. By setting the rear electrodesat differing voltage potentials, various color effects (such as colorcombinations) may be achieved.

In one embodiment, a pixelated rear electrode is created by providing adielectric substrate of one or more layers in which multiple electrodescorresponding to the same color are provided on a single layer andconnected in parallel. Alternatively, the pixelated electrodes can beprovided on a single substrate.

In another embodiment, the drawing system 150 includes a display media154 comprising a red region 154 a, a green region 154 b, and a blueregion 154 c as substantially described with respect to FIG. 14a, and amovable rear electrode 152 which addresses one of the three regions 154a, 154 b, 154 c at a time. When the movable rear electrode 152 is placedadjacent a region, an electric field is applied to that region todisplay the color of that region. A mechanical switch can be used tomove the electrode.

The embodiments of FIGS. 14a and 14 b are provided as examples only.Other embodiments for providing a color display can be used inaccordance with the present invention. Commonly-owned, co-pending U.S.patent application Ser. No. 09/140,862 filed Aug. 27, 1998, whichdescribes color electrophoretic displays is incorporated herein byreference.

Referring to FIG. 15a, a display 200 includes a rear electrode 202, adisplay media 204, a front electrode 206, and a touchscreen 208. Thetouchscreen 208 is disposed adjacent the front electrode 206.Alternatively, the touchscreen 208 can be laminated to or integratedwith the display media 204. For example, one of the electrodes of thetouchscreen can be applied directly on the front electrode 206 of thedisplay 200. Touchscreens which operate through resistive and capacitiveeffects are known to those skilled in the art. In this embodiment, thedisplay 200 is activated when a drawing instrument is pressed againstthe touchscreen 208. Alternatively, the touchscreen can be positionedbehind the drawing system.

In one embodiment, the display of the present invention is incorporatedinto a data capture mechanism, such as a credit card authorizationterminal. In this embodiment, a user signs his or her signature on adrawing surface of the display, and his or her signature is captured anddigitized. In one example, the stylus or data source emits wirelesswaves that are received by a sensing mechanism underneath themicroencapsulated electrophoretic layer and bottom electrode. In anotherexample, the flexibility of the microencapsulated electrophoretic layeris utilized to permit localized pressure to transfer through the displaymedia to a pressure-sensitive array or touch screen-type device in frontof or behind the display media. One advantage of this embodiment is thatwhile the signature or data tracing may be digitized at a coarseresolution, its image is displayed in analog by the display media athigher resolutions. In another example, the stylus or data source emitsinfrared or visible signals that transfer through the display media to asensing mechanism; here the wide temperature operating range ofmicroencapsulated electrophoretic displays is useful. In anotherexample, the stylus transmits acoustic waves that are again sensed by amechanism behind the display media. The sensing mechanism describe abovecan provide information about the location of the instrument on thedisplay.

Referring to FIG. 15b, the display 160 includes an electrostaticprinting mechanism. The electrostatic printing mechanism is included ina sliding bar 162, which may have one or more electrodes. The electrodesare connected to a driving mechanism such as an integrated circuit. Theelectrodes can also be connected to a data source such as a data storagedevice or a communications device. The communications device can be, forexample, a pager, a receiver, a modem, an infrared port or direct cableconnection. The sliding bar 162 can further include logic circuitry andposition sensors. In this embodiment, the sliding bar can be used as amanual or automatic electrostatic print head and can transfer images tothe drawing screen when the user slides the sliding bar 162. The system100 can further include mechanical or optic speed sensing device todetect the manual scanning of the print head.

The display 160 of FIG. 15b allows a user to download and display animage on the drawing screen. The image can be text (newspaper, book,e.g.), a dotted line image, a partial image, an image from a scrapbookor database, or even an interactive series of images. When equipped witha communications device and appropriate logic circuitry, the drawingdevice thereby can serve as a low-cost information display device suchas an extremely cheap web browser.

In another embodiment, the sliding bar 162 supports a scanning device.The scanning device can digitize the image provided on the screen of thedrawing system. When used in combination with a data storage device,memory device, or communications device, this will allow the drawingsystem to store, recall and transmit images. Alternatively, an externalscanning device can be used with the display 10 system.

In one embodiment, the sliding bar 162 slides across the screen as shownin FIG. 16a or is manually moved across the screen as shown in FIG. 16gto erase, scan, or draw. Alternatively, the screen of the drawing systemcan be moved relative to an electrode to perform the same functions. Forexample, the screen can be provided in a conveyor belt-likeconstruction, where the screen moves as shown in FIG. 16b, or where theelectrode moves as shown in FIG. 16d. Alternatively, the screen can bepulled out of a roll of display media as with a window shutter as shownin FIG. 16f, or the screen can be pulled through the sliding bar fromside to side as shown in FIGS. 16c and 16 e.

Referring to FIG. 17, a display system 170 includes a clear rearconductive electrode 172, a photoconductive dispersion layer 173, anencapsulated display media 174, and a top electrode 176. By providing aclear rear electrode 172, a photoconductive layer 173, and by addingappropriate logic, the display system 170 can “pick up” images fromlight-reflecting or light-emitting sources. The light 178 from an imagedisplayed on a light-reflecting or light-emitting source strikes thephotoconductive layer 173, causing the rear electrode 172 along with thetop electrode 176 to apply an electric field across the display media174, and thereby reproduce the picked up image on the display system170. The means for generating the electric field can be built internallyor externally to the display system. The system 170 can further includea light source (e.g., fluorescent light) for illuminating the substratewhich reflects the light. The light-reflecting substrate can be paper.The details of a display system including a photoconductive electrodeare provided in commonly-owned co-pending U.S. patent application Ser.No. 09/272,716, filed on Mar. 18, 1999.

In one embodiment in which the display system 170 lacks a top electrode176, the user of the display system 170 can hold the display system 170up to a light emitting display, such as a television or computer screen,move a sliding bar described above (not shown) across the top surface ofthe system 170, and thereby cause the display system 170 to reproducethe image on the television or computer screen. In another embodiment,in which the display system 170 includes the top electrode 176, the usersimply places the display system 170 in front of the television orcomputer screen to capture the image shown on the television or computerscreen. Alternatively, a light source internal or external to thedisplay system 170 can illuminate a substrate and capturelight-reflecting from the substrate, thereby copying the image on thesubstrate. Such system can be used as a toy, or as a novel way oftransporting temporary images. For instance, a user can hold anelectronic paper to his or her computer screen, image his or her day'sagenda, and then carry this paper throughout the day.

The term “display” and the term “drawing system” have been usedinterchangably herein. Both terms include devices capable of providingdrawing, copying, printing, or erasing functions. The term “movableelectrode” as used herein includes a writing device, an eraser, aprinter, or a scanner. The “movable electrode” also refers to anelectrode capable of moving relative to a display surface by eithermoving the electrode or moving the display.

While the invention has been particularly shown and described withreference to specific preferred embodiments, it should be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A drawing and display system for mounting on awall, the system comprising: a base member adapted for mounting on asubstantially vertical wall; an electrophoretic display media attachedto the base member and comprising a plurality of capsules, each capsulecomprising a plurality of electrophoretic particles in a suspendingfluid, the display media having a first surface and a second surface; arear electrode disposed adjacent the second surface of the displaymedia; a movable electrode comprising an electrostatic print head, inconjunction with the rear electrode, applying an electric field acrossthe display media, the applied electric field sufficient to cause atleast one of the electrophoretic particles to move and to print anelectronic image viewable through the first surface; and wherein thefirst surface comprises a drawing surface capable of being marked withan additional image by a dry-erasable marker.
 2. The system of claim 1wherein the movable electrode is a writing instrument.
 3. The system ofclaim 1 wherein the movable electrode comprises a stylus.
 4. The systemof claim 1 wherein the movable electrode is a charge generator.
 5. Thesystem of claim 1 wherein the movable electrode further comprises asensor that senses a location-indicating data on the first surface ofthe display media.
 6. The system of claim 5, wherein thelocation-indicating data sensed by the sensor assists the electrostaticprint head in printing a pre-determined image on the first surface ofthe display media.
 7. The system of claim 6 wherein the movableelectrode is capable of erasing at least a portion of the printed image.8. The system of claim 1 wherein the movable electrode further comprisesa speed sensor.
 9. The system of claim 1 further comprising adry-erasable marker.
 10. The system of claim 1 wherein the first surfacecomprises a protective layer.
 11. The system of claim 1 furthercomprising an optical input means.
 12. The system of claim 11 whereinthe optical input means comprises a scanner.
 13. The system of claim 11wherein the optical input means comprising a sliding bar that slidesacross the first surface of the display media.
 14. The system of claim 1wherein the display media further comprises a binder.
 15. The system ofclaim 1 wherein the movable electrode further comprises a charge storagedevice.
 16. The system of claim 1 wherein the movable electrode furthercomprises an eraser.
 17. The system of claim 1 wherein the movableelectrode comprises a plurality of electrodes insulated from each other.18. The system of claim 1 wherein the movable electrode furthercomprises a dielectric coating.
 19. The system of claim 1 wherein atleast a portion of the movable electrode comprises an elastomericmaterial.
 20. The system of claim 1 further comprising a dielectriclayer disposed adjacent the first surface of the display media.
 21. Thesystem of claim 1 further comprising a piezoelectric film disposedadjacent first surface of the display media.
 22. The system of claim 1wherein the movable electrode comprises a switch that reverses theelectric field applied to the display media upon activation of theswitch.
 23. The system of claim 22 wherein a color displayed on thefirst surface of the display media changes upon activation of theswitch.
 24. The system of claim 1 wherein the movable electrode has afirst end and a second end, wherein the display media displays a firstcolor when the first end is disposed adjacent the first surface of thedisplay media and a second color when the second end is disposedadjacent the first surface of the display media.
 25. The system of claim1 wherein the rear electrode comprises a polymer layer and a conductivecoating.
 26. The system of claim 1 further comprising a logic circuitfor driving the electrostatic print head.
 27. The system of claim 1further comprising a casing removable from the display media.
 28. Thesystem of claim 1 further comprising a belt loop.
 29. The system ofclaim 1 further comprising a permanent image on the first surface of thedisplay media.
 30. The system of claim 1 wherein the plurality ofelectrophoretic particles comprise a plurality of colors, and whereinthe rear electrode comprises a plurality of pixel electrodes, each pixelelectrode being set at a voltage for displaying particles of a selectedcolor on the first surface of the display media.
 31. The system of claim1 wherein the rear electrode is movable.
 32. The system of claim 1wherein the rear electrode comprises a first region and a second region,a voltage applied to the first region being different from a voltageapplied to the second region.
 33. The display of claim 32 wherein thevoltage applied to the first region of the rear electrode issubstantially the same as the voltage applied to the movable electrode.34. The system of claim 1 wherein the display media is bistable.
 35. Thesystem of claim 1 wherein at least one of the plurality of capsules issurrounded by a polymeric capsule wall.
 36. The system of claim 1comprising a polymer-dispersed electrophoretic display where theplurality of capsules are disposed in a polymer matrix.
 37. A method forcreating an image on a display system mountable on a wall comprising thesteps of: a) providing a display system comprising a base member adaptedfor mounting on a substantially vertical wall, an electrophoreticdisplay media attached to the base member and having a first surface anda second surface, the display media comprising a plurality of capsules,each capsule comprising a plurality of electrophoretic particles in asuspending fluid, the display further comprising a rear electrodedisposed on the second surface of the display media; b) placing amovable electrode adjacent the first surface of the display media, themovable electrode comprising an electrostatic print head; c) applying anelectric field across the display media through the movable electrodeand the rear electrode, thereby creating a first image on the firstsurface of the display media through movement of at least one of theparticles; and d) marking a second image on the first surface with anon-electric marker.
 38. The method of claim 37 further comprising thestep of sensing a location of the movable electrode on the first surfaceof the display media and creating a pre-determined image on the sensedlocation.
 39. The method of claim 37 further comprising the step oferasing at least a portion of the first image using an electrode. 40.The method of claim 37 further comprising the step of sensing the speedof a motion of the movable electrode.
 41. The method of claim 37comprising using a dry-erasable marker as the non-electric marker.